1. Field of the Invention
The present invention relates to a patient position monitor which senses and records the position and range of movement of a patient's body parts with respect to gravity.
2. Description of the Prior Art
Bed bound patients, such as those in nursing homes and other long-term care facilities, who are too ill or too weak to roll over in bed frequently get pressure ulcers from the occlusion of blood flow caused by pressure compressing soft tissues between bony prominences and the bed. Once formed, pressure ulcers are expensive to heal. Pressure ulcers can be prevented by regular turning of the patient in bed to relieve pressure from the compressed tissue. A turning intervention program by caregivers may be prescribed. Typical turning intervention programs call for repositioning the patient every two hours around the clock.
Although turning intervention programs often are prescribed to periodically relieve pressure of compressed tissues, they are not always successful for a variety of reasons. Turning interventions may be delayed or omitted because of situational exigencies or due to a lack of understanding by nursing staff of the clinical consequences of missed or delayed interventions.
Patients who are confined to a bed are not necessarily completely immobile. Some such patients spontaneously turn themselves, but self-turning is not predictable or regular, thus self-turners also require intervention during some parts of the day. Moreover, it is difficult, if not impossible, for the nursing staff to determine when a patient last spontaneously turned. Patient records are not maintained on such spontaneous turning even if they are known to occur. In other circumstances, the nursing staff will turn a patient and the patient at some point will subsequently turn back to the original more comfortable position, making the pressure relieving turn ineffective.
Turning intervention programs are prescribed for around the clock turnings, thus patients usually awake from nighttime sleep when being turned. Some patients who do receive turning intervention may be turning on their own and thus, their sleep is unnecessarily disturbed by nursing staff complying with the prescribed turning intervention during the night.
Even when written turning intervention schedules are prescribed, a combination of caregivers' lack of perception of the consequences of missed interventions, inadequate patient risk assessment tools to determine who truly needs turning intervention and flawed nursing care management practices together account for the failure of such intervention programs to minimize the development of pressure ulcers of mobility impaired residents of nursing care facilities.
Another aspect of the mobilization of patients living in long-term care facilities is the frequency and duration that the patients stand or walk each day. Because some patients require physical restraints for medical reasons or to ensure their physical safety, they may be forced to remain in chairs by use of belts, vests, jackets, trays, bars, and the like. Once restrained, oftentimes these patients are not freed to stand or move for long periods of time either because it is difficult for the nursing staff to know when a patient was last moved or simply due to nursing staff convenience or neglect. According to current health care practice, patients restrained in a seated position should be permitted to or assisted to stand or walk for at least 10 minutes every two hours.
Devices which detect the movement of a person by a prescribed degree have been described previously. For example, a device which monitors the sleep posture of a patient and provides an alarm for generating a stimulus to awaken the person if movement has not been detected from that particular posture in a prescribed amount of time is disclosed in U.S. Pat. No. 4,617,525. The sleep posture monitor includes a position sensor capable of detecting movement from a single position. Neither the position of the patient relative to gravity nor the subsequent positions are recorded.
A similar device is disclosed in U.S. Pat. No. 3,163,856. A wrist-worn motion detector is used to determine whether a person has not moved within a given period of time. In one embodiment, the wrist-worn motion detector comprises a conductive ball contained in an annular raceway which connects adjacent pairs of electrodes. Motion by the patient causes the ball to roll about the raceway to make and break adjacent pairs of contacts. An alarm is sounded if no movement is detected for a certain period of time. This motion sensor detects movement by a patient, but there is no indication of the direction of movement and actual position of the patient or the duration of time spent in each position.
A patient position monitor which detects the change in the angle of position of a patient such as occurs when a patient has fallen from a bed or chair or the like is disclosed in U.S. Pat. No. 4,348,562. A mercury switch is secured to a patient to detect when the patient has moved from a horizontal to vertical position. The mercury switch comprises a two-chambered body where the chambers are connected by a passageway having a slope through which a ball of mercury can only pass from a first chamber to a second chamber (which contains electrodes) when the patient has moved from a horizontal to a vertical position to an angle beyond 40 to 70 degrees. An electrical circuit is completed only when the patient raises sufficiently from a horizontal position for the ball to enter the second chamber and close the circuit.
An apparatus for monitoring patient activity comprising an angle inclination sensing means mounted to a patient's legs is disclosed in U.S. Pat. No. 4,536,755. The sensing means comprises a mercury switch which is actuated when the switch is oriented in a downward position when the patient is standing vertically. Contact of the mercury with two electrodes occurs whenever a predetermined inclination threshold angle is exceeded.
Neither of these devices monitor the rotation of the patient's torso and its position relative to gravity. They provide information only when the patient moves beyond a predetermined position and do not monitor the time spent in a particular position.
Despite these advances in patient position monitoring, a need remains for a patient position monitor which detects the duration of each position assumed by a patient reclining in bed relative to gravity and provides data on the past positions of the patient relative to gravity along with the degree of change of the patient's position and duration of time in each position to diagnose the need for turning intervention programs and to assist nursing staff in the implementation of turning intervention programs. A need also remains for a patient position monitor which detects the movement of a patient from a horizontal to a vertical position and the duration of time in each position.